Oil scavenge system having churning damper for gas turbine engines

ABSTRACT

An oil scavenge system of a gas turbine engine in accordance with one embodiment of the present invention, comprises a housing defined about an axis of rotation, the housing confining an air/oil mixture in motion within the housing and defining an oil scavenge area below the axis of rotation. The housing further includes an outlet at a low location of the housing. A churning damper is supported within the housing and is located in the oil scavenge area. The churning damper includes at least one plate, allowing the air/oil mixture in motion to pass over or through the plate only in a peripheral area of the at least one plate to cause flow energy dissipation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Division of Applicant's U.S. patent application Ser. No.11/692,287 filed on Mar. 28, 2007.

TECHNICAL FIELD

The invention relates generally to oil systems for gas turbine enginesand more particularly, to an improved oil scavenge system.

BACKGROUND OF THE ART

Gas turbine engines for aircraft typically include a gear box containinga gear train drivingly connected to an engine main shaft and auxiliarycomponents. The gear box is also connected in an oil system of theengines which lubricates and cools the gear train within the gear box.Gear train rotation generates a high velocity and unsteady flow of highdensity air/oil mixture inside the gear box, which can blast oil off thecollecting areas onto the moving parts. The oil collecting and blastingprocesses within the gear box reach an equilibrium when very littleliquid oil is left in the collecting areas. The high density air/oilmixture circulating inside the gear box generates heat by churning, in amanner similar to that of a dynamometer water brake. Baffles areconventionally used around one or more gears within the gear box and areconfigured for the purpose of deflecting oil blasting away from thecollecting areas.

Accordingly, there is a need to provide an improved oil scavengingsystem to improve oil collecting and reduce heat generated by thechurning of the air/oil mixture within the gear box.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide an oil scavengesystem of a gas turbine engine.

In one aspect, the present invention provides an oil scavenge system ofa gas turbine engine which comprises a housing defined about an axis ofrotation, the housing confining an air/oil mixture in motion within thehousing and defining an oil scavenge area below the axis of rotation,the housing including an outlet at a low location of the housing; and achurning damper supported within the housing and located in the oilscavenge area, the churning damper including at least one plate,allowing the air/oil mixture in motion to pass over or through the plateonly in a peripheral area of the at least one plate to cause flow energydissipation.

In another aspect, the present invention provides an oil scavenge systemof a gas turbine engine which comprises a housing defined about an axisof rotation, the housing confining an air/oil mixture in motion withinthe housing and defining an oil scavenge area below the axis ofrotation, the housing including an outlet at a low location of thehousing; and means having peripheral edges substantially increased inlength relative to a damping surface area defined by the peripheraledges, for causing flow energy dissipation of the air/oil mixture inmotion when passing towards the outlet from the damping surface areaover the substantially increased peripheral edges, the means beinglocated in the oil scavenge area to separate liquid oil from the air/oilmixture and to discharge the liquid oil through the outlet.

In a further aspect, the present invention provides a gear box of a gasturbine engine which comprises a housing having an outlet fordischarging oil contained in the housing; a gear train operationallysupported within the housing; and a churning damper supported within thehousing and located between at least a part of the gear train and theoutlet, the churning damper including a plate with holes extendingthrough a thickness of the plate, the individual holes having a diameterequal to or smaller than the thickness of the plate.

Further details of these and other aspects of the present invention willbe apparent from the detailed description and figures included below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures depicting aspects ofthe present invention, in which:

FIG. 1 is a schematic cross-sectional view of a turbofan gas turbineengine as an example illustrating an application of the presentinvention;

FIG. 2 is a partial and elevational cross-sectional view of a gear boxof the gas turbine engine illustrated in FIG. 1, incorporating oneembodiment of the present invention to show a churning damper supportedwithin the gear box;

FIG. 3 is a partial cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a top plane view of the churning damper in accordance with theembodiment of FIGS. 2 and 3, showing a plate of the churning damperhaving perforations with preferable dimension ratios;

FIG. 5 is a top plane view of a plate of the churning damper accordingto another embodiment of the present invention, showing a peripheralarea of the plate having holes extending through the plate;

FIG. 6 is a top plane view of a plate of the churning damper accordingto a further embodiment of the present invention, showing a peripheralarea of the plate having increased peripheral edges in a saw-toothconfiguration;

FIG. 7 is a top plane view of a plate of the churning damper accordingto a further embodiment of the present invention, showing a peripheralarea of the plate having increased peripheral edges in a rectangulartooth configuration;

FIG. 8 is a cross-sectional view of a plate of the churning damperaccording to a further embodiment of the present invention, showing theplate having a corrugated configuration; and.

FIG. 9 is a top plane view of a plate of the churning damper accordingto a still further embodiment of the present invention, showing amulti-plate configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a gas turbine engines as an example of theapplication of the present invention, which includes a housing ornacelle 10, a core casing 13, a low pressure spool assembly seengenerally at 12 which includes a fan assembly 14, a low pressurecompressor assembly 16 and a low pressure turbine assembly 18 and a highpressure spool assembly seen generally at 20 which includes a highpressure compressor assembly 22 and a high pressure turbine assembly 24.The core casing 13 surrounds the low and high pressure spool assemblies12 and 20 in order to define a main fluid path (not indicated)therethrough including a combustor 26.

Reference is now made to FIGS. 1 and 2. The gas turbine engine furtherincludes an auxiliary gear box 30 which includes a housing 32 secured toa bottom mounting face (not indicated) of nacelle 10. A gear train (notindicated) is operatively supported within the housing 32. The geartrain includes a pair of bevelled gears 34 and 36 to connect a towershaft 28 which in turn is drivingly connected to the high pressure spool20. The gear train of the gear box 30 is also drivingly connected tovarious engine devices such as a pump assembly, a starter generator,etc. (not shown), such that the driving power provided by the highpressure spool 20 is distributed through the gear train of the gear box30 to said engine devices. The gear box 30 is also connected, forexample by tubes, to an oil system of the gas turbine engine. Liquid oiland/or air/oil mixtures collected from bearing compartments (not shown)are delivered into the gear box 30 to cool and lubricate the gear train.The air/oil mixture within the gear box 30 may be further separated forexample by an air/oil separator 38 mounted to one shaft of the geartrain The recovered liquid oil is then delivered by the oil scavengingsystem of the present invention, from the gear box before being reused.

Referring to FIGS. 2-4, a churning damper 40 generally includes a plate42 supported by for example, a plurality of braces 44 within the housing32, in accordance with one embodiment of the present invention. Theplate 42 may be flat or slightly curved. The plate 42 is mounted to thehousing 32 and is located in an oil scavenging area 46 within thehousing 32. The oil scavenging area 46 is defined in a lower portion ofthe housing 32 below the gear train and is in communication with anoutlet 48 which is also located in a low part of the housing 32 and isin fluid communication with, for example an oil sump (not shown) of theengine oil system. The plate 42 is dimensioned and shaped to extendbetween at least a part of the gear train and the outlet 48, but causesno interference with the operation of the gear train. For example, inaccordance with the illustration of FIGS. 2 and 3, the plate 42 extendslaterally past gear 34 and another co-axially mounted gear (notindicated).

In this embodiment, the plate 42 includes a plurality of holes 50 whichare optionally distributed over the substantially entire plate 42. Thegear train rotation causes high velocity motion of the air/oil mixturewithin the housing 32. This high velocity motion of the air/oil mixtureresults in an unsteady flow of the air/oil mixture within the housing32, which can blast liquid oil collected on the surfaces of stationaryparts of the gear box (which are referred to as the collecting areas)back onto the moving parts of the gear train, thereby increasing thedensity of the air/oil mixture until the oil collecting and blastingprocesses result in a density equilibrium when very little liquid oil isleft in the collecting area. The dense air/oil mixture circulationinside the gear box 30 generates heat by churning.

The plate 42 located in the oil scavenging area 46, interferes with theflow pattern of the air/oil mixture inside the housing 32, dampening theflow fluctuations and deflecting the flow of air/oil mixture away fromthe collecting areas. The upper side of the plate 42 forms a dampingsurface area to collect the oil suspension and flow energy dissipationfurther occurs as the dampened air/oil mixture passes through the holes50. A high flow velocity gradient through the holes 50 contributes tothe oil suspension coalescing into large particles which separate fromthe air/oil mixture under gravity. The separated liquid oil collected onthe plate 42 falls into and is collected around the outlet 48 from whichthe liquid oil is then discharged back to the oil system of the engineby the connected sump. The resulting leaner air/oil mixture forms arelatively steady circulation with lower velocity and thus generatesless heat and blasts less liquid oil from the collecting areas.

The individual holes 50 in the plate 42 in this embodiment, arepreferably designed to have a relatively small diameter and relativelylarge spaces therebetween, in order to reduce the chance of the highvelocity air/oil mixture passing directly through the individual holes50 upon impinging on the plate 42, without being dampened by the dampingsurface area of the plate 42. For example, the individual holes 50 mayhave a diameter equal to or less than the thickness of the plate 42 andthe holes 50 are spaced by a distance equal to or greater than threetimes the diameter of the individual holes 50. The plate 42 should havea thickness such that the plate 42 has enough rigidity to preventvibration during engine operation when the plate 42 is supported by alimited number of said braces 44.

In FIG. 5 the churning damper 40 in accordance with another embodimentof the present invention, includes a plate 42 a as an alternative to theplate 42 in FIGS. 2-4. Plate 42 a includes holes 50 a distributed onlyin a peripheral area of the plate 42 a, to form a strip of perforationsalong peripheral edges of the plate 42 a. Therefore, the middle portionof the plate 42 a which forms a central blank region prevents the highvelocity air/oil mixture from passing through the plate 42 a, from thedamping surface area (the upper side of the plate 42 a) towards theoutlet 48 of FIG. 2, and only the perforated peripheral area of theplate 42 a allows the air/oil mixture to pass through the plate via theholes 50 a and the peripheral edges of the plate 42 a. The high velocityimpingement of the air/oil mixture on the plate 42 a more likely occursin the middle portion of the plate 42 a because of the location of thechurning damper 40 within the gear box 30 with respect to the positionof the gear train. However, there are no holes in the middle portion ofthe plate 42 a to allow the high velocity air/oil mixture to passtherethrough without being dampened by the damping surface area of theplate 42 a. According to this embodiment, as depicted in FIG. 5, thecentral blank region is sized greater than the spacing between theadjacent rows of the holes 50 a. It is also depicted that the perforatedstrip is narrower than the width of the central blank region.

In FIG. 6 the churning damper 40 in accordance with a further embodimentof the present invention includes a plate 42 b as an alternative toplate 42 in FIGS. 2-4 and to plate 42 a of FIG. 5. The plate 42 bdefines a peripheral area with peripheral edges 52 substantiallyincreased in length relative to the surface area of the plate 42 bdefined within peripheral edges 52, in contrast to the strip of holes 50a shown in FIG. 5. The substantially increased peripheral edges 52defined in the peripheral area of plate 42 b, which is shown in FIG. 6as an example, is achieved by peripheral edges 52 being configured in asaw-tooth pattern. The high velocity air/oil mixture inside the gear boxof FIGS. 2 and 3 is dampened by the damping surface area (the upperside) of the plate 42 b and is directed along the damping surface areato pass over the edges 52, thereby causing flow energy dissipation atthe plate edges 52. The saw-tooth configuration substantially increasesthe length of the peripheral edges 52 of the plate 42 b in contrast to,for example, peripheral edges in straight lines as in the plates 42 ofFIG. 4 and plates 42 a of FIG. 5, thereby causing flow energydissipation at the edges 52 to be more efficient.

FIG. 7 illustrates a still further embodiment of the present inventionin which the churning damper 40 includes a plate 42 c. As an alternativeto plate 42 b of FIG. 6, plate 42 c defines a peripheral area withperipheral edges in a rectangular tooth configuration to increase thelength of the peripheral edges 52.

It should be noted that the substantially increased peripheral edges ofthe plate 42 b illustrated in FIG. 6 may be optionally combined with theperforated plate 42 shown in FIG. 4 or the partially perforated plate 42a shown in FIG. 5 to achieve even more efficient energy dissipation.Alternative to plates 42, 42 a, 42 b and 42 c illustrated in therespective FIGS. 4, 5, 6 and 7 which are flat or slightly curved, theplates 42, 42 a, 42 b and 42 c can have a corrugated configuration as inplate 42 d, illustrated in FIG. 8. Furthermore, plate 42 d may beoptionally incorporated with the features of perforations andsubstantially increased edges 52 as described in the previousembodiments. It should also be noted that the corrugated plate 42 d ispreferably configured to avoid forming deep grooves which will causesignificant accumulation of liquid oil on the damping surface area (theupper side) of the plate 42 d.

In FIG. 9 the churning damper 40 in accordance with a further embodimentof the present invention includes a plurality of plates 42 e which arealigned with one another in one plane, with gaps 54 in combination toform a damping surface area (the upper side of the plates 42 e)substantially equivalent to the damping surface area of plates 42, 42 a,42 b and 42 c described in the previous embodiments. Each of the plates42 e is securely supported within the housing 32 of the gear box 30 ofFIGS. 2 and 3. The peripheral edges (not indicated) of the individualplates 42 e in combination, form the increased peripheral edges of thechurning damper 40. Therefore, the high velocity air/oil mixture insidethe gear box of FIGS. 2 and 3, is dampened in the damping surface areaof the individual plates 42 e and is directed to pass through the gaps54 such that flow energy dissipation occurs at the peripheral edges ofthe individual plates 42 e. A total length of the peripheral edges ofthe individual plates 42 e is significantly greater than the outerperiphery of the churning damper 40, thereby efficiently improving flowenergy dissipation.

It should be noted that the features described in the previousembodiments may also be optionally incorporated with the embodimentillustrated in FIG. 9.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departure from the scope of the invention disclosed.For example, the oil scavenging system of the present invention isdescribed with reference to the embodiments of the gear box of a gasturbine engine. However, the oil scavenging system of the presentinvention is also applicable to other devices of a gas turbine engine,such as a bearing compartment of an engine shaft. Still othermodifications which fall within the scope of the present invention willbe apparent to those skilled in the art, in light of a review of thisdisclosure, and such modifications are intended to fall within theappended claims.

The invention claimed is:
 1. An oil scavenge system of a gas turbine engine comprising: a housing defined about an axis of rotation, the housing confining an air/oil mixture in motion within the housing and defining an oil scavenge area below the axis of rotation, the housing including an outlet at a low location of the housing; and a plate having peripheral edges in a saw-tooth configuration to form increased peripheral edges of the plate to surround a damping surface area of the plate for causing additional flow energy dissipation of the air/oil mixture in motion when passing towards the outlet from the damping surface area over the increased peripheral edges, the plate being located in the oil scavenge area to separate liquid oil from the air/oil mixture and to discharge the liquid oil through the outlet.
 2. An oil scavenge system of a gas turbine engine comprising: a housing defined about an axis of rotation, the housing confining an air/oil mixture in motion within the housing and defining an oil scavenge area below the axis of rotation, the housing including an outlet at a low location of the housing; and a plurality of plates aligning in one plane with gaps between the plates, the plates in combination forming a damping surface area and peripheral edges of the individual plates forming increased-in-length peripheral edges of the damping surface area for causing additional flow energy dissipation of the air/oil mixture in motion when passing towards the outlet from the damping surface area over the increased-in-length peripheral edges, the plates being located in the oil scavenge area to separate liquid oil from the air/oil mixture and to discharge the liquid oil through the outlet.
 3. An oil scavenge system of a gas turbine engine comprising: a housing defined about an axis of rotation, the housing confining an air/oil mixture in motion within the housing and defining an oil scavenge area below the axis of rotation, the housing including an outlet at a low location of the housing; and a plate having peripheral edges in a rectangular tooth configuration to form increased-in-length peripheral edges of the plate to surround a damping surface area for causing additional flow energy dissipation of the air/oil mixture in motion when passing towards the outlet from the damping surface area over the increased-in-length peripheral edges, the plate being located in the oil scavenge area to separate liquid oil from the air/oil mixture and to discharge the liquid oil through the outlet. 